package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    // 将任意对象写入redis并设置TTL
    public void set(String key, Object value, Long time, TimeUnit timeUnit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, timeUnit);
    }

    // 将任意对象写入redis并设置逻辑过期时间
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit timeUnit) {
        // 设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(timeUnit.toSeconds(time)));
        // 写入Redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    // 解决缓存穿透
    public <T, ID> T queryWithPassThrough(
            String keyPrefix, ID id, Class<T> cls, Function<ID, T> dbFallback,
            Long time, TimeUnit timeUnit) {
        // 1.根据key从redis中查询缓存
        String key = keyPrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);
        // 2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            // 3.存在，直接返回数据
            return JSONUtil.toBean(json, cls);
        }
        // 4.判断命中的是否为空值
        if (json != null) {
            return null;
        }
        // 5.不存在，根据id查询数据库
        T t = dbFallback.apply(id);
        // 6.该数据不存在，返回空值
        if (t == null) {
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        // 7.存在，写入redis
        this.set(key, t, time, timeUnit);
        return t;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <T, ID> T queryWithLogicExpire(String keyPrefix, ID id, Class<T> cls, Function<ID, T> dbFallback,
                                          Long time, TimeUnit timeUnit) {
        // 1.从redis查询商铺缓存
        String key = keyPrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);
        // 2.数据已经预热，直接判断是否存在
        if (StrUtil.isBlank(json)) {
            // 3.不存在，直接返回
            return null;
        }

        // 4.命中，把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        T t = JSONUtil.toBean((JSONObject) redisData.getData(), cls);
        LocalDateTime expireTime = redisData.getExpireTime();
        // 5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            // 5.1.未过期，直接返回信息
            return t;
        }
        // 6.已过期，进行缓存重建 获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        boolean isLock = tryLock(lockKey);
        // 6.1.判断是否获取互斥锁成功
        if (isLock) {
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    // 查询数据库
                    T newR = dbFallback.apply(id);
                    // 重建缓存
                    this.setWithLogicalExpire(key, newR, time, timeUnit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    // 释放锁
                    unlock(lockKey);
                }
            });
        }
        // 7.返回旧数据
        return t;
    }


    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }

}
